When applying high-voltage direct current to a pin-to-plane electrode geometry with a distance of 2 mm under atmospheric pressure in argon gas, electrical breakdown forms primary then secondary streamers. The polarity of the applied voltage affects this streamer-propagating phenomenon. Properties such as propagation speed, streamer head size, and plasma generation are parameterized at nanosecond scales by computational simulations of a self-consistent, multi-species, multi-temperature plasma fluid modeling approach. For positive polarity on the pin electrode, streamer-head propagation speeds up and streamer head size increases with increasing applied voltages. However, local electron density at the head decreases. For negative polarity, corona-like discharges form around the pin electrode under low applied voltages, and diffusive steamers form under high applied voltages. Secondary streamers re-propagate from the pin after primary streamer propagation, forming a plasma with a high electron density of 1021 m−3 for the positive polarity. We show that low-voltage operations with positive polarity are useful for stable high-electron-density discharges under atmospheric pressure argon.

By using a stacked mask process (S-MAP) with spun-on-carbon (SOC) film, 38 nm line patterns were successfully etched by controlling the ion energy using high-bias-frequency dual-frequency-superimposed (DFS) rf capacitively coupled plasma in combination with the low hydrogen content SOC film. It was found that ions with higher energy enhance the fluorination of SOC and induce pattern wiggling under fluorine exposure. By using a higher bias frequency to control the ion energy distribution and reduce the maximum ion energy, the SOC pattern wiggling was effectively suppressed.

Surface-enhanced rewnance Raman scattering spectra (SERRS) in the region below 500 cm-' were recorded for the manganese(II1) and chromium(II1) tetraphenylporphine complexes (TPP)Mn"'X (X = Cl-, CIOL) and (TPP)Cr"'X (X = Cl-, Clod-) adsorbed on a silver electrode surface in acetonitrile (ACN). The surface spectra in the low-frequency region clearly reflect changes in the axial ligation states of the metalloporphines associated with the adsorption process involving the silver electrode. On adsorption to the electrode at 0 V (vs Ag/AgCl), (TPP)MnI'ICI dissociates the fifth axial ligand (a chloride ion), forming an adsorbed species, [(TPP)MnIl']+. On the other hand, (TPP)Cr"'CI retains the chloride ion as a fifth axial ligand on the electrode surface at 0 V.Upon a negative sweep of the electrode potential, the chloride complex gradually disappears, forming [(TPP)Cr"I]+; the disappearance is completed at -0.4 V. A SERRS spectrum obtained for a divalent manganese TPP complex adsorbed on a silver electrode proved that the adsorbate is a four-coordinated species; in contrast, the divalent manganese complex in ACN exists as a five-coordinated complex possessing an associated solvent molecule as a fifth ligand (i.e., (TPP)Mn"(ACN)). IntroductionSurface-enhanced resonance Raman scattering (SERRS) spectroscopy has been recognized as one of the most sensitive techniques to observe the vibrational spectra of various chromophore~,~-~ including heme proteinse and chlorophyllsgJO adsorbed on coinage metals such as silver and gold. Its high sensitivity permits acquisition of the vibrational spectra of adsorbates even at a surface coverage less than a monomolecular layer. Surface spectra have been measured also for synthetic metalloporphines adsorbed on silver ele~trodes,~~-'~ silver and roughened silver surfaces;I6 the results revealed characteristic features of their surface processes including redox reactions and metal-insertion and -exchange reactions.In the present paper, we report the SERRS spectra of adsorbates on a silver electrode for manganese(II1) and chromium(II1) tetraphenylporphines having an axially coordinated monoanion, such as chloride and perchlorate, in acetonitrile (ACN); the

For the precise control of the ion energy in reactive ion etching (RIE), a 1-MHz pulsed-direct current (DC) square-wave-superimposed (p-DCS) 100-MHz radio frequency (RF) capacitively coupled plasma (CCP) is studied and compared with a 13.56- and 100-MHz dual-RF-superimposed (DFS) CCP. The proposed CCP is applied in RIE for sub-32-nm node etching of spun-on-carbon using H2-based gas at 2.66 Pa and 1200 W of 100-MHz RF power. A minimum critical dimension shift of 3 nm is achieved at high etch rates in p-DCS CCP using an optimized square-wave voltage of −750 V, compared with a corresponding shift of 9 nm in DFS CCP using 400 W of 13.56-MHz RF power. Because the maximum of the ion energy distribution (IED) is controlled by the square-wave voltage and more than 70% of the total ion flux is concentrated in a narrow range around the maximum ion energy, the CCP offers precise control of the IED, which is effective in the RIE of the fine-patterned devices.

A new method of generating obliquely incident ions has been investigated. A plasma system with a cathode consisting of a repetition of a group of four electrode rods connected to their respective RF power supplies is proposed. The ion angular distribution (IAD) is controlled by modulating the phase shift of the four RF powers. The IAD of an argon high-density plasma was analyzed on the basis of transient plasma simulation. When the RF voltages are controlled so that the phase shift is π/2, a convex-shaped plasma sheath corresponding to each group of four rods appears and propagates parallel to the wafer with time. By propagating this “wavy” sheath, a bimodal IAD consisting of ions obliquely incident mainly from two directions are obtained nearly uniformly across the wafer. This method is capable of generating obliquely incident ions, which is expected to be effective as an additional knob for precise profile control in fine-pattern reactive-ion etching (RIE).